1. Field of the Invention
The present invention pertains to cellular telecommunications, and particularly to allocation of data resources in a cellular telecommunications system.
2. Related Art and Other Considerations
In recent years cellular telephones have become increasingly popular. A cellular telephone is just one example of what is referred to in telephone parlance as a xe2x80x9cmobile stationxe2x80x9d or xe2x80x9cmobile terminalxe2x80x9d. Telecommunications services are provided between a cellular telecommunications network and a mobile station (e.g., cellular telephone) over an air interface, e.g., over radio frequencies. At any moment an active mobile station is in communication over the air interface with one or more base stations. The base stations are, in turn, managed by base station controllers (BSCs). The base station controllers are connected via control nodes to a core telecommunications network. Examples of control nodes include a mobile switching center (MSC) node for connecting to connection-oriented, circuit switched networks such as PSTN and/or ISDN, and a general packet radio service (GPRS) node for connecting to packet-switched networks such as Internet, for example.
A mobile station can take on various forms other than a cellular telephone, including a computer (e.g., a laptop computer) with mobile termination capabilities. In some forms, mobile stations are capable of engaging in differing types of services, or multimedia services. In other words, the mobile station can execute several differing types of programs (i.e., xe2x80x9capplicationsxe2x80x9d) which interact with the user. Examples of these applications include Internet browsers and electronic mail programs. Several multimedia applications may reside in the same mobile station.
One type of standardized mobile telecommunications scheme, utilized, e.g., in Europe, is the Global System for Mobile communications (GSM). GSM includes standards which specify functions and interfaces for various types of services. A relatively recent data service available within the GSM system is General Packet Radio Service (GPRS). GPRS differs from existing data services in that GPRS is a packet switched service instead of a circuit switched data service. Whereas (in GSM) a circuit switched data user is connected continuously to the radio network during a data call (e.g., even when not transferring data), a GPRS user is connected to the radio network only when either (1) the mobile station desires to transmit or (2) the network has something to transmit to the mobile station. In other words, in GPRS the mobile station (e.g., a computer with mobile termination) is not connected to the network constantly while the computer is in use, but only during these two transmission events.
For the purpose of data services in cellular time division multiple access (TDMA) systems, packet data services such as GPRS are used alongside existing circuit-switched services. Since the existing radio band cannot be expanded, packet data services must be fitted into the same band as circuit-switched services. Thus, a certain amount of capacity has to be taken from circuit switched services for packet data services. Additionally, as circuit-switched services have been predominate, the introduction of packet data services must not degrade the quality of service for the existing circuit switched services.
The GPRS service is provided to a connection over a GPRS packet data channel (PDCH). GPRS has two types of packet data channels: (1) the MPDCH, or master packet data channel (which carries broadcast information, paging messages, access grant messages, and user information), and (2) the SPDCH, or slave packet data channel (which carries user information and associated signalling). A time slot in the radio base stations can dynamically be configured, for instance as a TCH/F (speech traffic channel), MPDCH, or SPDCH.
Radio resources are allocated dynamically. For speech traffic, the radio resource is a full-rate speech time slot (TCH/F) and for data traffic the resource is a block called PDTCH, which is sent on a PDCH. The packet data channel resources are limited, therefore efficient use of these resources is essential when a radio resource is configured as a PDCH.
Methods of dynamically allocating speech and data resources are known. For example, PCT publication WO96/22665 discloses a method of determining the number of time slots allocated to a packet data service and to a circuit switched service by dynamically allocating more time slots to the form of service having the greater demand at any particular time. A nominal basic number of time slots is reserved for packet radio service and another number of time slots is reserved for circuit switched service. If the traffic requires for packet radio service increases, information regarding the increase is obtained through a request flagged by a mobile station or through traffic measurement by the base station. The information is used as criteria in the allocation of more time slots to the requiring such slots.
Once a packet data channel has been configured for data traffic, the packet data channel must be efficiently utilized in view of the limited packet data resources. Therefore, what is needed, and an object of this invention, is an efficient technique for allocating packet data channels among users.
In a cellular telecommunications system, a method of dynamically allocating packet data radio channels among users competing in a same cell for the channels involves determining a user ranking for each of plural competing users in the cell, and classifying each of the plural competing users into one of plural ranking classes. A number of the packet data radio channels available for each of the ranking classes is then determined, after which the users within each ranking class are sorted by ranking. The packet data radio channels are allocated to the users by sorted position within ranking classes.
The user ranking for each of the plural competing users in the cell is related to a weighted combination of plural measures of performance for the user. In general, the user ranking for a user is determined in accordance with the combination ru=a1f1(x1u)+a2f2(x2u)+ . . . +aMfM(xMu), in which there are M different measures of performance for each user; the performance measures being represented by a vector (x), and which includes ranking weighting-functions, fm and ranking weighting-constants, am.
In one embodiment, the plural measures of performance for the user include at least two of the following: (1) user priority; (2) maximum delay relative to a target maximum delay value; (3) remaining time relative to a transmission time in higher layers; (4) an assigned bit rate relative to a target bit rate value; (5) a number of remaining packets relative to a target number of remaining packets; (6) a number of recent transmission failures; (7) a required output power value relative to a target output power value; (8) a radio link quality value relative to a target radio link value; and (9) normalized packet delay.
The step of allocating the packet data radio channels to the users by sorted position within ranking classes can be performed by various techniques of the present invention. According to a first technique, the channels are awarded to the users in descending ranking order within each ranking class. In accordance with a second technique, a limiting number of packet data radio channels available to a particular ranking class is determined and, to the users in the particular ranking class, the limiting number of packet data radio channels are awarded in descending ranking order within the particular ranking class.